Thermosensitive self-plugging bentonite and preparation method thereof and water-based drilling fluid

Abstract

The present disclosure relates to a thermosensitive self-plugging bentonite, a preparation method thereof, and a water-based drilling fluid.

The invention claimed is: 
     
       1. A water-based drilling fluid, comprising a mud slurry, a thermosensitive self-plugging bentonite, sodium chloride, an anionic carboxymethyl cellulose, a zwitterionic polymer, calcium carbonate, and pentaerythrityl tetrastearate;
 wherein the thermosensitive self-plugging bentonite has a network structure formed by interleaving bentonite crystal layers, a flexible functional modifying agent is bonded on the surface of the crystal layers and between two adjacent crystal layers, the flexible functional modifying agent is at least one selected from the group consisting of N-isopropylacrylamide, methyl methacrylate, ethyl acrylate, benzyl methacrylate, N,N,N′,N′-tetramethylethylenediamine, acrylic acid and a stabilizer; 
 wherein the thermosensitive self-plugging bentonite is 12-20 g, the sodium chloride is 3-9 g, the anionic carboxymethyl cellulose is 1.5-3 g, the zwitterionic polymer is 1.5-3 g, the calcium carbonate is 9-15 g, the pentaerythrityl tetrastearate is 0.6-1.5 g, and water is 300-500 mL, based on the total weight of the water-based drilling fluid. 
 
     
     
       2. The water-based drilling fluid of  claim 1 , wherein the flexible functional modifying agent is 10-20 wt % based on the total weight of the thermosensitive self-plugging bentonite. 
     
     
       3. The water-based drilling fluid of  claim 1 , wherein the stabilizer is a mixture of anionic carboxymethyl cellulose and polyamide-amine type dendrimer. 
     
     
       4. The water-based drilling fluid of  claim 1 , wherein the thermosensitive self-plugging bentonite has an opening-closing temperature within a range of 80-140° C. 
     
     
       5. The water-based drilling fluid of  claim 4 , wherein the thermosensitive self-plugging bentonite has an opening-closing temperature within a range of 120-140° C. 
     
     
       6. The water-based drilling fluid of  claim 1 , wherein the thermosensitive self-plugging bentonite has an average particle size of 300-500 meshes. 
     
     
       7. A method for preparing the water-based drilling fluid of  claim 1 , comprising a step of preparing the thermosensitive self-plugging bentonite, wherein the step of preparing the thermosensitive self-plugging bentonite comprises the following steps:
 (1) mixing bentonite and concentrated hydrochloric acid and dissolving bentonite in the concentrated hydrochloric acid, and performing rotary distillation treatment; then subjecting the treated product to washing, drying and grinding treatment, so as to produce an activated bentonite; 
 (2) dispersing the activated bentonite in water, then carrying out a first contact with a silane coupling agent to obtain a first mixed solution; subjecting the first mixed solution and chloroform to a miscible process, and performing centrifugation and washing treatment; 
 (3) dispersing the product obtained from step (2) in water, then subjecting the product to a second contact with one or more selected from the group consisting of N-isopropylacrylamide, methyl methacrylate, ethyl acrylate, benzyl methacrylate, and N,N,N′,N′-tetramethylethylenediamine to obtain a second mixed solution; and the second mixed solution and acrylic acid or acrylic ester polymer monomer are subjected to a polymerization addition reaction; 
 (4) subjecting the product obtained from step (3) to a third contact with the stabilizer to obtain a third mixed solution, and subjecting the third mixed solution to drying, hot rolling and grinding treatment, thereby prepare the thermosensitive self-plugging bentonite. 
 
     
     
       8. The method of  claim 7 , wherein, the conditions of miscibility in step (1) comprise: the temperature is within a range of 35-45° C., and the time is 5-8 h;
 wherein the conditions of the rotary distillation comprise: the temperature is within a range of 100-120° C., and the time is 5-9 h; 
 wherein the drying conditions include: the temperature is within a range of 80-90° C., and the time is 2-4 h; 
 wherein the bentonite is used in an amount of 2-3 g relative to 100 mL of concentrated hydrochloric acid; 
 wherein the concentrated hydrochloric acid has a concentration of 30%; 
 wherein the activated bentonite has an average particle size of 300-500 meshes. 
 
     
     
       9. The method of  claim 7 , wherein the dispersing conditions in step (2) comprise: the ultrasonic frequency is within a range of 30-35 KHz, the ultrasonic power is 1.5-1.7 w/cm, and the ultrasonic time is 3-5 h;
 wherein the conditions of the first contacting include: the temperature is within a range of 50-58° C., and the time is 2-3 h; 
 wherein the conditions of the centrifugation comprise: centrifuging at 7000-9000 rpm for 3-5 min; 
 wherein the silane coupling agent is one or more selected from the group consisting of 3-glycidyloxypropyltrimethoxysilane, (3-aminopropyl) trimethoxysilane and gamma-methacryloxypropyltrimethoxysilane; 
 wherein the activated bentonite is 5-10 g, the silane coupling agent is 1-2 g, and the chloroform is 30-50 mL, relative to 100 mL of water. 
 
     
     
       10. The method of  claim 7 , wherein in step (3), the conditions of the second contacting comprise: stirring for 20-30 min under the protection of nitrogen and a condition of ice water bath;
 wherein the reaction conditions include: the temperature is within a range of 65-70° C., and the time is 5-8 h; 
 wherein, the product obtained from step (2) is 3-5 g, the N-isopropylacrylamide is 4-7 g, and the N,N,N′,N′-tetramethylethylenediamine is 2-5 g, relative to 200 mL of water; 
 wherein the volume ratio of the second mixed solution to the acrylic acid and acrylate polymer monomer is 1:(1.15-4.25):(0.2-0.5). 
 
     
     
       11. The method of  claim 7 , wherein the conditions of the drying hot rolling in step (4) comprise: the temperature is within a range of 120-130° C., and the time is 24-48 h;
 wherein the stabilizer is a mixed solution of anionic carboxymethyl cellulose and polyamide-amine type dendrimer; and the volume ratio of the anionic carboxymethyl cellulose to the polyamide-amine type dendrimer is 1:(2-5); 
 wherein the stabilizer is 2-5 mL relative to 200 mL of water. 
 
     
     
       12. The method of  claim 7 , wherein the thermosensitive self-plugging bentonite has an average particle size of 300-500 mesh. 
     
     
       13. The water-based drilling fluid of  claim 1 , wherein the water-based drilling fluid further comprises barite powder, the barite powder has an average particle size of 200-500 meshes.